1. Technical Field
The present disclosure relates to a keyless entry device of a vehicle capable of carrying out radio communications between a portable device carried by a driver and the vehicle and performing locking or unlocking of a door without using a key.
2. Related Art
There is generally known a technique in a keyless entry device that automatically unlocks a door without a key operation by authenticating a corresponding one of plural antennas, which are installed in an in-vehicle device forming a search range of a portable device in a vicinity area outside a vehicle through radio waves, and the portable device through communication when unlocking of the door is requested (for example, see JP-A-2008-121254 (FIGS. 3 and 4).
In this known technique, when one door (for example, the door of a passenger's seat) is opened by the authentication in a certain search range, a detection range (for example, the vicinity of the door in the rear of the passenger's seat and the vicinity in the front of the passenger's seat) adjacent to the search range is continuously searched. When the detection range of detecting the portable device is changed, a detection range (for example, the vicinity of a backdoor, the vicinity of the door in the rear of a driver's seat, or the vicinity of the door of the driver' seat) adjacent to the detection range is continuously searched. Finally, when a detection range of the door of the driver's seat is reached without interruption of the search of the portable device, the door of the driver's seat is opened without a special operation.
In the known technique, the detection range of detecting the portable device and a detection range adjacent to the detection range continue to be searched after the unlocking of the door is performed. When the detecting of the portable device is stopped in all the detection ranges, the doors are all unlocked. For example, when a passenger carrying the portable device approaches and opens a door and when the passenger moves away from the vehicle later, the door can be unlocked automatically. This makes it convenient for the passenger and safety is increased.
When the portable device is not detected in any of the detection ranges in the vicinity of the vehicle, as in the known technique, a control method of locking the door is generally performed. In the known control method, however, the locking of the door is not generally performed when the portable device is detected inside the vehicle. The reason for performing this control is to prevent the door from being locked in a state where the portable device is present inside the vehicle (when a driver has forgotten to carry the portable device and has locked the door) and this control takes a priority over all conditions.
For this reason, when general control logic is designed to prevent the door from being locked, the control logic is performed in the following sequence. (1) It is confirmed whether a portable device is present inside a vehicle. When it is confirmed that the portable device is present, the search ends and locking of a door is not performed. (2) When it is confirmed that the portable device is not present, the search for the portable device is subsequently searched for in the vicinity outside the vehicle. When it is confirmed that the portable device is present, the portable device is continued in the vicinity outside the vehicle and the locking of the door is not performed. (3) Alternatively, when it is confirmed that the portable device is present in the vicinity outside the vehicle, the locking of the door is performed. According to this control logic, the locking of the door is not performed as long as it is confirmed that the portable device is present inside the vehicle. Therefore, it is expected that the portable device will not be locked inside erroneously.
In the control logic, however, when the driver carrying the portable device is getting off the vehicle and moving fast away from the vehicle, a chance of confirming the presence of the portable device may be missed at a time at which the portable device is present in the vicinity outside the vehicle for a certain time. That is, when the driver carrying the portable device is getting off the vehicle fast after the driving and is moving away from the vehicle at a speed exceeding a normal walking speed, the presence of the portable device cannot be confirmed in spite of first searching for the portable device inside the vehicle. This is because the driver has already gotten off the vehicle. Thereafter, when the portable device is searched for in the vicinity outside the vehicle, the presence of the portable device cannot be confirmed due to the fact that the driver carrying the portable device has already moved out of the detection range at this timing.
In effect, even when the driver carrying the portable device is away from the vehicle, the locking of the door may not be performed according to the control logic due to the fact that the portable device is not present anywhere. In this case, since the door of the vehicle is left unlocked according to the general control logic, the safety may not be ensured.
When the presence of the portable device cannot be confirmed in either the outside or the inside of the vehicle, it is not desirable to use a control logic in which the door is simply locked for reasons of the safety. This control logic has a problem in that the door is left unlocked in the state where the portable device is put inside the vehicle when communication with the portable device fails.
For example, it is supposed that the driver has gotten off the vehicle and moved away from the vehicle in the state where the portable device is put inside the vehicle. In this case, when radio interference or operation failure (deterioration in a battery capacity or the like) of the portable device occurs at timing at which the portable device is first searched for inside the vehicle, the presence of the portable device cannot be confirmed according to the control logic even in a case where the portable device is actually present inside the vehicle. Subsequently, the portable device is searched outside the vehicle. However, since the portable device has not been taken out to the outside of the vehicle, the presence of the portable device cannot be confirmed. In this case, the locking of the door is performed due to the priority of the safety according to the control logic. Therefore, the locking of the door may be performed carelessly in the state where the portable device is put inside the vehicle.